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Plastic -Definitions
Some ubiquitous `mers' are ethylene, styrene and acrylamide. Each of these may be polymerized to make, respectively, polyethylene (the soft clear plastic that plastic bags are made of), polystyrene (the stiffer, usually white plastic that the covers for soft-drink cups are made of), and polyacrylamide (the very tough, clear plastic that compact discs are made from).
Look on the bottom of a recyclable plastic bottle - chances are you will see a PE or PS which means polyethylene or polystyrene. These materials are examples of what happens to polymers when they solidify: the chains are entangled and packed together to make light, tough, flexible materials.
A way to think about some of these materials is to think of what a big glob of cooked spaghetti is like. If you stretch it a bit, it is kind of elastic, but if you really pull hard, the noodles start to slide past one another and the whole glob starts to permanently deform. At least that is the idea! Does this remind you of what happens to a PE plastic bag when you stretch it? Think about what must be happening to the microscopic spaghetti that the bag is made up of!
This way of thinking doesn't work very well to describe stiffer plastics like PS: the chemical units in stiffer plastics are actually packed together in a orderly way, into pseudo-crystals.
If you heat up PE or PS to moderate temperatures, if the chains have not been chemically stuck together (`cross-linked') they will melt, and turn into goopy liquids, which are called polymer melts. Some polymers are melts even at room temperature, like polydimethylsiloxane(PDMS), or poly(ethylene-propylene) (PEP).
Remembering that paper is made of cellulose, which is a polymer of biological origin, if you look around
the room that you are in, you will see that a good fraction of the stuff in it is made of polymers. And of
course, you are, too!
Polymer Etymology
The word comes from Greek: poly means `many' and mer comes from merous which roughly means `parts'. Our word polymeric comes directly from the Greek polumeres which simply means `having many parts'
